Modern communication units (e.g., mobile phone hand sets) include integrated antennas configured to transmit and receive radio frequency (RF) signals. Integrated antennas are sensitive to external use cases (e.g., whether a hand is positioned on the phone, the position of a hand on the phone, etc.) that alter the impedance of the integrated antenna, leading to an impedance mismatch between the antenna and RF circuitry within a transmitter. Such an impedance mismatch can degrade the power radiated by a communication unit and increase the communication unit's sensitivity to noise. From a user's perspective, impedance mismatches can ultimately lead to a reduction in talk time or a dropped call. To provide better matching between RF circuitry in the transmitter and the antenna, handset designers use antenna tuners.
Conventionally, handset designers have arranged sensors inside the phone's package to detect the presence or absence of external use cases in an environment. Then the detected environment is compared with known use cases (e.g., “free space”, “hand on the phone”, “close to head”, “metal plate” . . . ) and a corresponding predetermined antenna tuner setting is chosen based on the detected use case. Unfortunately, this conventional approach requires a large number of sensors inside the mobile phone, which increases the phone's size and cost (particularly if there are a large number of possible use cases to be detected). Alternatively, a feedback receiver may be configured to determine an impedance of an output signal from a measured amplitude and phase of the output signal, and to adjust the antenna tuner settings based upon the determined impedance.